In a semiconductor device (semiconductor package), with a tendency of more multi-step layers of semiconductor chips, a higher density of an internal wiring, and a thinner package, a package whose sealing resin on semiconductor chips has a thickness of approximately 100 to 150 μm is required. With regard to resin sealing of a semiconductor chip, in transfer molding, there occurs a problem that a resin cannot be sufficiently filled on the semiconductor chip in a case of a package having a sealing resin with a thin thickness on the semiconductor chip, or there occurs a problem that a short circuit occurs between wirings due to deformation of a metal wire in a case of high density internal wiring with the metal wires. In order to solve the above problems, application of compression molding to resin sealing of a semiconductor chip is considered (see JP-A 2004-056141 (KOKAI) and JP-A 2006-088619 (KOKAI)).
In compression molding, for example, a thermosetting resin composition in granular form generated in a process to manufacture a tablet of the thermosetting resin composition (sealing resin material) to be used in transfer molding is used. A conventional granular thermosetting resin composition (sealing resin material) is fabricated as follows, for example. First, respective materials of an uncured thermosetting resin, a curing agent, a filler and the like are weighed and mixed, and the mixture is kneaded. A kneading step is performed while heating to approximately 100° C. in general so that the respective materials are uniformly mixed. On this occasion, some resins reside for a long time in the kneading step, and there is a possibility that a curing reaction proceeds and a cured product is generated. Such a cured product is called an acetone insoluble matter.
Next, a kneaded product of the respective materials is extended to form a sheet, cooled and then ground, whereby the granular sealing resin material (uncured thermosetting resin composition) is fabricated. In the grinding step of the kneaded product, a particle diameter of the resin composition is approximately several ten μm to 2 mm in general. Thus, if the sealing resin material contains a cured product (acetone insoluble matter) of the thermosetting resin, its particle diameter varies from approximately several ten μm to 2 mm. In a sealing resin material generally used, a cured product (acetone insoluble matter) of a thermosetting resin is contained at a rate of several ten ppm.
If resin sealing of a semiconductor chip by compression molding is performed by using the granular sealing resin material described above, there may be caused a problem such that the cured product (acetone insoluble matter) of the thermosetting resin contained in the sealing resin material damages the semiconductor chip or deforms an internal wiring by a metal wire. In a compression molding method, a semiconductor chip is disposed in a cavity of a sealing apparatus and a sealing resin material is supplied thereon. A thermosetting sealing resin material is heated while being pressurized. The sealing resin material fluidized by pressurizing and heating is filled in the cavity.
On this occasion, if the sealing resin material contains an acetone insoluble matter with a large particle diameter, a large pressure is locally applied on the semiconductor chip via the acetone insoluble matter sandwiched between the semiconductor chip and a pressuring mold. The above causes a scratch, a crack or the like in the semiconductor chip. If the acetone insoluble matter with the large particle diameter exists between an internal wiring by a metal wire and a pressurizing mold, there is a possibility that the pressurizing mold presses the acetone insoluble matter against the internal wiring, thereby deforming the internal wiring. In a thinned semiconductor device, there is a tendency that a thickness of a sealing resin on a semiconductor chip is made thinner. In such a case, in particular, an acetone insoluble matter tends to give an adverse influence to the semiconductor chip or an internal wiring.
Further, based on an increase of density or improvement of function of a semiconductor chip, in an internal wiring (metal wire) electrically connecting the semiconductor chip and a wiring substrate or the like, a layout pitch is tend to be minuter. If a sealing resin material contains an acetone insoluble matter with a large particle diameter, there is a possibility that the acetone insoluble matter sandwiched between the neighboring metal wires deforms the metal wire, causing a short circuit between the metal wires. Further, even if a short failure does not occur, there is a possibility that a leak occurs between the neighboring metal wires. The short failure or the like between the metal wires due to the acetone insoluble matter may occur not only in resin sealing by compression molding but also in resin sealing to which transfer molding is applied.